Fig. 2
Deformation structures along the northwestern DBBT. a Folded contact between rocks of the Dent Blanche nappe and the structurally lower Combin zone in the eastern Val de Zinal; quartz-rich rocks of the Dent Blanche nappe are folded while the greenschist-facies foliation of Combin calcschists partly represents an axial planar foliation and is partly folded as well. b Combin calcschists in the eastern Val de Zinal showing ductile top-SE shear bands. c Combin calcschists in the footwall of the DBBT near Lac d’Arpitetta showing ductile top-SE shear bands. d Overturned gneisses of the lowermost Dent Blanche nappe near Arolla. e Sample FD118: Gneiss from the base of the Dent Blanche nappe near Arolla; a GSPO of quartz grains indicates a top-W sense of shear; Fol (272/23) Lin (272/23); crossed polarizers. f Sample FD293: Gneiss from the base of the Dent Blanche nappe near Arolla; quartz layers show dynamic recrystallization by SGR and partly display 120° triple junctions; shear sense criteria in this sample indicate a top-WNW shear sense; Fol (347/46) Lin (285/26); crossed polarizers. g Sample FD07: Polished hand-specimen of a mylonite from the DBBT east of the village Ollomont in the Valpelline of Italy; Fol (88/23) Lin (119/19) crenulation axes (47/17); note small-scale shear zone in the middle with a crenulation cleavage in the upper part and drag folds directly below. h BSE-picture of zoned epidote: an allanite core is surrounded by distinct zones of relatively Fe-rich, Fe-poor, and another Fe-rich epidote; numbered points correspond to epidote measurements in Online Resource 2. i Equilibrium phase diagram calculated with the THERIAK-DOMINO software package (De Capitani and Petrakakis 2010) with excess water (30 H2O) and additional oxygen (1 O2); see text for discussion; solution models: feldspar, quartz, epidote, amphibole, biotite, lawsonite, hematite, magnetite: Berman (1988); white mica: Keller et al. (2005b); chlorite: Hunziker (2003); omphacite: Meyre et al. (1997); glaucophane: Evans (1990); numbered assemblages: (1) Ab + Ph + Omp + Hem + Lws + Qtz + Gln; (2) Ab + Ph + Omp + Tr + Hem + Lws + Qtz; (3) Ab + Ph + Omp + Tr + Hem + Lws + Qtz; (4) Ab + Ph + Pg + Omp + Ep + Hem + Qtz; (5) Ab + Ph + Pg + Ep + Prg + Hem + Qtz; 6) Ab + Ph + Pg + Ep + Prg + Hem + Mag + Qtz; (7) Ab + Ph + Ep + Prg + Hem + Qtz; (8) Ab + Ph + Chl + Ep + Prg + Hem + Qtz; (9) Ab + Ph + Pg + Chl + Ep + Prg + Hem + Qtz; (10) Ab + Ph + Pg + Chl + Ep + Hem + Qtz; (11) Ab + Ph + Chl + Ep + Hem + Qtz; mineral abbreviations according to Whitney and Evans (2010). j Combin calcschists in the footwall of the DBBT near Ollomont showing ductile top-SE shear bands